The present invention relates to a storage control device.
A storage control device is a device which supplies a storage region of comparatively large capacity to a host computer (hereinafter termed a “host”). A storage control device may, for example, construct a storage region on the basis of RAID (Redundant Array of Independent Disks), using a plurality of hard disk drives. Logical volumes, which are logical storage regions, are established over the physical storage regions possessed by the hard disk drives. The host is able to perform reading and writing of data to and from these logical volumes.
Now, a storage control device is per se known (see JP-A-2007-011682) in which a main chassis which is in charge of control functions and an extension chassis which is in charge of storage functions are connected in a daisy chain. A controller and a plurality of hard disk drives are mounted in the main chassis, and a plurality of hard disk drives are mounted in the extension chassis.
With a prior art storage control device, according to requirements, the user can increase the storage capacity of the storage control device by adding extension chassis. However, the more extension chassis are added, the more does the size of the storage control device increase. Furthermore, if the number of storage devices which are provided in the extension chassis is increased, the amount of heat which is generated also increases. Accordingly, although it is necessary to obtain a draft of cooling air which is matched to this amount of heat, if simply the rotational speed of a cooling fan is increased, then the noise also becomes great.
When a lid unit which covers over an opening portion is removed, the cooling air draft passages within the chassis and this opening portion communicate with one another, and air flows into the cooling air draft passage from the opening portion, whose flow resistance is comparatively low. Due to this, the flow of the draft of cooling air changes, and there is a possibility that the cooling air draft will not be adequately supplied to at least some of the storage devices, so that they will not be properly cooled.
In particular, for example with the so called drawer method which makes it possible to take out a storage device or the like from the upper surface of a chassis like a drawer and to put it back in, if maintenance work is to be performed without stopping the operation of the storage control device, then the above described problem of the cooling air draft appears prominently. In this case when, for maintenance work, the lid unit is removed, then the cooling air draft passages within the chassis communicate with the opening portion so that the flow of the draft of cooling air is changed, and regions occur where the draft of cooling air is not supplied. Accordingly, it is not possible to perform maintenance work over a long time period, i.e. it is necessary to complete any maintenance work in a short time period, so that the convenience of use decreases. This is because, the longer becomes the time period over which the lid unit is removed, the more does the temperature of the storage device or devices to which the cooling air draft is not adequately supplied become elevated, so that it is possible for problems due to high temperature to occur.